Oven thermometer



H. R. WHITIIER. OVEN THERMOMETEB. APPLICATION FILED mm. 23, 1 921.. RENEWED SEPT. 16, m2.

1,432,936. Patented Oct. 24, 1922,

Patented Oct. 24, 1922.

UNITED, STATES PATENT OFFICE.

' HORACE R. WHITTIER, OF PLYMOUTH, CONNECTICUT.

OVEN THERMOMETER.

Application filed April 23, 1921, Serial No. 463,822. Renewed September 16, 1922. Serial No. 588,730.

To allwhomitmag concern:

Be it known that I, HORACE R. VVHITTIER, a citizen of the United States, residing at Plymouth, in the county of Litchfield and State of Connecticut, have invented anew and useful Improvement in Oven Thermometers, of which fication.

This inventionrelates to the class of ther- I crate the pointer steadily and uniformly according to the degrees of heat during all portions of its path.

This object is attained by loosely mount ing the thermostatic strip that is connected with the pointer upon a bridge or spindle holder so that it is free to expand and contract according to the, temperature uniformly in all positions that is, the strip is only influenced by the temperature and is at no time required to overcome tension or mechanical resistance as would be the case if the strip was tightly fixed at one end.

In the accompanying drawings Fig. 1 shows a plan of the casing and activemechanism of a thermometer which embodies the invention. Fig. 2'sl1ows a section onthe plane indicated by thedotted line 2-2 on Fig. 1. I Y

The casing comprises a jflat back plate 1, designed to be secured to the wall of the oven or other part of the chamber, the temperature of which is to be indicated, anda cylindrical. side wall 2. which with the back plate and cover that is omitted, surrounds and encloses the active mechanism.

The act-ivemechanism is mounted on the bridge plate 3 that is fastened to the inside of the back plate by rivets or other conventhe following is a speci is madeot common thermoresponsive metal, the opposite sides of which have different coeiiicients of expansion. The other ends of the thermoresponsive strip are hinged to a pm 9 that projects from the arm 10 which s fixed to the pointer spindle. This arm 10 1s provlded witha number of holes 11, into either of which the pin 9 may be set for calibrating the device according to the required conditions.

' The curved form of the thermostatic stri provides a greater degree of expansion than a straight strip and by reason of the loose connections of the strip at its ends it may swing and assume a natural position as the curvature changes during expansion and contraction and thus there is no tendency of mechanical strains to resist the change of shape of the strip, a condition which would result if the strip were rigidly connected to its support as in prior structures of this type. Furthermore, this arrangement permits the strip to be directly connected with the arm projecting from the spindle and eliminates the necessity of interposing a link connection. In making this device the parts are all assembled on the bridge plate and then the plate is simply inserted into the casing and fastened in position.

The invention claimed. is: 1. A thermometer comprising a casing, a

plate secured to the inside of the casing. a

pointer spindle supported bythe plate, an arm fixed to the spindle, a post projecting from the plate parallel with the spindle, a pin projecting from the arm parallel with the post, and a curved thermo-responsive strip with one end loosely hinged on the post and the other end loosely hinged on the pin whereby the strip mayturn freely on the post and pin and expand and contract uniformly in all positions under the varying temperature conditions.

2. A thermometer comprising a casing, a plate secured tothe inside of the casing. a pointer spindle supported by the plate, an arm with perforations fixed to the spindle, a post projecting from the plate parallel with the spindle, a curved thermo-responsive strip with one end loosely hinged on the post and a pin loosely hinged to the other end of the thermo-responsive strip, said pin being adapted to be inserted into either of the per- 1 forations of said arm. 

